Summary On 2 June 1999 at about 0045 local time, the loaded chip barge Rivtow901, under tow of the tug SheenaM, struck the Canadian Pacific Railway Mission Railway Bridge which spans the Fraser River at Mission, British Columbia. The striking caused considerable damage to the protection pier and swing span of the bridge. Rail traffic over the bridge was interrupted until 30June 1999. Marine traffic through the swing span was suspended until the same date when it was made available on a limited basis. Unrestricted maritime use of the swing span was not available until 26July 1999. Ce rapport est galement disponible en franais. Factual Information Particulars of the Vessels Description of the Vessels Tug SheenaM The SheenaMis a steel tug with the superstructure forward and a towing winch located on the centre line of the main deck behind the superstructure. Two diesel engines driving two reversible propellers constitute the propulsion system which is entirely controlled from the wheelhouse. The towing winch on the SheenaMis situated on the after deck, approximately one-third of the vessel's length from the stern. The drum of the towing winch contains approximately 180m of 250mm diameter tow wire connected to two 220mm diameter towing bridles, each approximately 13m in length. The towing winch is fitted with an electric-hydraulic abort system that can be activated remotely from three locations on the vessel. Chip Barge Rivtow901 The Rivtow901is a barge of all-welded steel construction designed for the on-deck carriage of wood chips in bulk. Steel bulwarks, 4.7m high, set in from the port and starboard sides of the barge form an open-topped cargo box with a smooth inboard face supported by exterior steel stanchions. Description of Canadian Pacific Railway (CPR) Mission Railway Bridge Constructed in 1909, the Canadian Pacific Railway (CPR) Mission Railway Bridge spans the Fraser River at Mission, B.C. Supported by 13concrete piers, the bridge is approximately 533m long. The swing span with a vertical clearance of 4.9m above Higher High Water Large Tide (HHWLT) when closed is fitted atop a circular concrete pier, the 10th from the north bank of the river. This concrete pier is protected by a treated wood pile, timber and wood sheathed protection pier extending upstream approximately 46 m and downstream, approximately 46m from the concrete pier. The protection pier is tapered at the up-river and down-river ends. The navigable portions of the north and south channels are approximately 30m wide. At night a fixed white light is displayed on piers9 and 11 as well as at the up-river and down-river ends of the protection pier. Marine traffic with low air draught requirements such as log tows, loaded and unloaded gravel barges, use the channel beneath the fixed span between piers5 and 6 for navigation. The swing span north and south channels are used mainly for wood chip barge traffic and other marine traffic that cannot navigate under the rail bridge between piers5 and 6. A bridge tender maintains an office on the shore at the north end of the bridge and is on duty around the clock. The bridge tender may be contacted by telephone and also monitors a VHF radio. When requested to open the bridge for marine traffic, the tender walks the trestle to a control booth situated on the swing span. The tender must remain on the swing span while the bridge is in the open position. History of the Voyage At 17452 on the evening of 1 June 1999, a relief master and deckhand set out by water taxi from Port Hammond, on the Fraser River, to relieve the crew of the tug SheenaM in the vicinity of Port Coquitlam, B.C. After a brief handover, the relief crew took over and the previous crew departed in the same water taxi. Neither the master nor deckhand is a full-time employee of the operator and, as such, is not employed on a regularly scheduled basis. However, they had received advance notice of this work and were reportedly well rested. The tug SheenaMwas upbound on the Fraser River, towing one empty chip barge. The master had been told by the tug owner to deliver the chip barge to the Meeker Cedar mill in Mission, B.C., exchange it for a loaded chip barge at the same mill, and then return down-river to await orders, the most likely destination suggested was Annacis Island, on the Fraser River. Aboard the SheenaMall equipment was reported to be in good working order. The moon was full on May30, the sky was clear and bright, visibility good. There was no appreciable wind. As part of the handover, the master had been informed that the gauge reading at Mission was 15.09feet (4.6m). This represents the height of the river level above chart datum. The 20-mile passage up the river was uneventful. Using a cellular telephone at approximately 2245, the master of the SheenaM gave the bridge tender on the CPR Mission Railway Bridge at Mission advance notice of the intentions of the SheenaM with an expected time of arrival (ETA) of 2330 at the bridge. The bridge tender advised the master that he was monitoring very high frequency radio-telephone (VHF R/T) radio channel80 and requested 20minutes notice for opening the span. Adhering to the bridge tender's instructions, the SheenaM arrived at the bridge at the given time and made the upstream passage through the south draw without event, arriving at the Meeker Cedar mill at approximately 2345 (see Figure 1). The Meeker Cedar mill is situated on the north bank of the Fraser River approximately 500 m upstream of the CPR Mission Railway Bridge. Upon arrival at Mission the crew of the SheenaM secured the empty chip barge to a dolphin adjacent to the mill. They then took the chip barge Rivtow901, loaded with approximately 2,100tonnes of wood chips, from under the loading chute at the mill to a position approximately 100m upstream on the same bank, securing it to a dolphin. Re-connecting to the empty barge they had brought with them, it was manoeuvred into position under the loading chute and secured. Upon completion they returned to the Rivtow901 and, after attaching their tow line and bridle, began their preparations for the passage down river. Approximate time of their departure from Mission, with the loaded chip barge in tow, was 0020 on June2. On departure the master of the SheenaMagain contacted the CPR Mission Railway Bridge tender, giving an ETA of 20minutes at the bridge. Figure 1. Map showing the location of the CPR Mission Railway Bridge. Proceeding upstream, stemming the current, the SheenaMand her tow crossed the Fraser River, using the lights of a mill on the north bank upstream of Meeker Cedar as reference before commencing a turn downstream toward the bridge. This reference point equates to an approximate sailing distance from the point of departure (near the mill) of 1000m and is upstream from the bridge, a distance of approximately 1400m. The master turned the SheenaMto port. When both tug and tow were heading downstream the master used a minimum throttle in order to maintain bare steerageway as he followed the south bank of the river toward the south draw of the bridge. The master's intention was to keep both tug and tow away from the main flow of the river, remaining as close to the south bank as possible. As the SheenaMmade her approach to the bridge the master was alone in the wheelhouse. The deckhand was standing by the winch controls on the after deck ready to respond to instruction from the master; the port wheelhouse door was open to facilitate communication. Both master and deckhand later reported that the lights on the CPR Mission Railway Bridge marking the navigable passages were dimly lit and difficult to discern. The master of the SheenaMreported that the shackle connecting the towing wire to the bridle was approximately 3.7 m abaft the stern. Combined with the bridles this gave an approximate distance of 15 m between the tug and barge. With the Rivtow901following the SheenaM so closely the master had no difficulty seeing the barge, given the brightness of the night. The master made full use of the helm, supplemented by short bursts of throttle, in his effort to keep the Rivtow901tracking astern of the SheenaM. As the SheenaMclosed on the south draw of the CPR Mission Railway Bridge, the master became aware of an increase in the strength of the current setting toward mid-channel. This had the effect of setting the barge further away from shore than the tug. Realizing he was committed to making the transit of the bridge, he redoubled his efforts, using both helm and throttle, in his attempt to achieve safe passage through the bridge. The SheenaM did not make contact with the bridge structure. However, the master suspected, by the feel of the tow transmitted to the tug through the tow wire, that the barge had made contact with the bridge structure. When the barge made contact, the progress of both vessels was momentarily arrested before continuing through the draw. The deckhand on the stern of the SheenaM reported that he heard first the sound of wood breaking, followed by the sound of metal working against metal. The time was approximately 0045 on the morning of June2. The master used VHF80 to call the bridge tender, asking if he was all right. Upon receiving an affirmative response he advised the bridge tender that the tug would return to pick him up. The SheenaMwith the Rivtow901 in tow continued through the draw and proceeded to a location on the north bank, approximately 1000m downstream from the bridge, known as the Herman grounds, to secure the barge. At approximately 0050 the master of the SheenaMcalled the vessel owner by cellular telephone, informing him of events. The damage sustained by the bridge was significant. Since the bridge tender must remain on the swing span when it opens, he was now isolated on that span with the fear that the structure might topple into the river at any moment, carrying him with it. Not being content to await the return of the SheenaM, the bridge tender contacted the water taxi service, whose base of operations is at Mission, adjacent to the bridge, with the request that he be immediately removed from the span. With the Rivtow901secured to a log boom at the Herman grounds at approximately 0100, the SheenaMwas then free to return to the bridge to pick up the bridge tender. When the SheenaMwas informed by the bridge tender that a water taxi was expected, the tug then travelled upstream through the north draw and returned downstream through the south draw. During her passage through the south draw her mast became fouled by an overhead cable. Moments afterward the mast carried way. This low-voltage overhead cable has an advertised vertical clearance of 21 m above chart datum, but when the bridge was struck, the cable supports were displaced resulting in a reduced vertical clearance of the cable. The SheenaMcontinued downstream through the draw and, through use of her spotlight, was able to provide illumination when the bridge tender was picked up by the water taxi. After the bridge tender was safely recovered, the SheenaMreturned to the Rivtow901in order to inspect her for damage. The barge was lying on an even keel and seemed to be watertight with no apparent damage to her hull. At 0130, after satisfying himself that the watertight integrity of the Rivtow901 was not impaired, the master of the SheenaMdecided to resume towing the barge down river to Annacis Island tie-up. The barge was secured to her lay-by berth at Annacis Island at 0530 ready for passage to her discharge berth on Vancouver Island. Injuries to Persons Damage Damage to the Vessel Damage to the tug was minimal. The low-voltage overhead cable spanning the draw was designed to provide an advertised clearance of 21m above chart datum. This became dislodged when the bridge was struck resulting in a significant reduction of clearance. The tug's main mast, fitted with navigation lights and radio antennae, became fouled in this cable after the accident and was carried away (see Figure 2). Figure 2. The tug SheenaM without mast. Damage to the Barge The most significant damage was to the upper edge of the steel box-wall on the starboard side which was fractured and set-in over a length of approximately 6m at a point immediately forward of the barge's mid-length (see Figure 3). Lesser damage was sustained by the vertical stiffeners welded to the external face of the box-wall. These were damaged to varying degrees, ranging from paint scuffs to, in the case of one stiffener, sufficient deformation to require replacement. The barge's hull remained intact. Only a small amount of the wood chip cargo was spilled onto the bridge or into the river. Figure3. The chip barge Rivtow901 with damaged starboard box-wall under repairs. Damage to the Bridge The upstream portion of the bridge protection pier was significantly damaged. As a result of the impact by the barge, the nose of the squared timber (upper) portions of the protection pier was deflected to the north. Without this protection, the swing span was dislodged from its pedestal by the barge impact and deflected approximately 4m to the west. Figure4. Damaged nose of protection pier deflected to north. Figure5. Damaged CPR Mission Railway Bridge at Mission, B.C., viewed from south shore of Fraser River. Meeker Cedar mill in background with a chip barge at loading facility. Damage to the Environment There was no environmental damage as a result of the striking. Certification Vessels The tug was built in B.C. in 1981, twin screwed and rated at 600 (brake horse power) bhp. Its gross tonnage of 9.99 is below the 10-tonne threshold above which requires Transport Canada inspection and certification. However, they must still be operated in compliance with all Regulations applicable to vessels in her trade. The SheenaMconforms with Fraser River industry norms in terms of size and power. All equipment at the time of the accident was reported to be in good working order. The vessel was acquired by her current owner in 1998 for use primarily on the Fraser River. As an unmanned barge built before 1 September 1977, and not carrying pollutants, the Rivtow901 is not subject to inspection by Transport Canada, Marine Safety. Personnel The master of the SheenaMholds a Master Home Trade 350 Ton Certificate of Competency issued by Transport Canada in 1970 and re-issued, with STCW3 endorsement in February 1992. This certificate was valid at the time of the occurrence. The deckhand held no certification nor was he required to do so. Personnel History The master's towing experience dates from 1958, all on west coast waters and the Fraser River. His first command was in 1964. Between 1958 and 1968 he sailed almost exclusively on this section of the Fraser River, during which time he estimates having made several hundred transits of the CPR Mission Railway Bridge. More recently he has been employed in towing construction materials on the coast. His last previous transit of the CPR Mission Railway Bridge was in 1990, but not during freshet4(see Current Information). Communications A Vessel Traffic Services (VTS) scheme, with mandatory Calling-in-Points (CIP), is in place near the mouth of the Fraser River. The section of the river in the vicinity of Mission, B.C., is outside that zone. In order to co-ordinate bridge openings, mariners first establish contact with the bridge tender by telephone then update their progress by means of VHF radio-telephone. Weather and Current Information Weather on Scene Weather conditions were fine and clear with little wind and calm seas in the sheltered waters of the Fraser River. Current Information Fraser River at Mission, B.C. In the late spring each year the Fraser River experiences freshet. During freshet the volume of water flowing through the Fraser River estuary increases from its winter low by a factor of 10. As the river level rises, the volume of water flowing past a given point increases significantly. In the spring of 1999, a combination of increased snow-pack inland combined with above average temperatures resulted in a freshet significantly above the norm. Throughout any given day the actual water levels can vary for a variety of reasons such as diurnal tidal effect, air temperature, and resultant rate of snow-melt. At the time of the accident the water level at Mission was closer to 4.5m above chart datum. This equates to an approximate discharge rate of 7950cubic metres per second (cms). By calculation this discharge rate can be expressed as a mean surface velocity, bank to bank, of 1.3metres per second (m/s) or approximately 2.5knots. Environment Canada hydrologists caution that the figure given is a mean, and particular sections of an unobstructed river might have a surface velocity of 1.7m/s or 3.3knots. When the normal flow of a river is obstructed by a bridge structure and the flow of water is guided through specific channels, surface velocities can increase appreciably above those for an unobstructed river. Environment Canada maintains a river level gauge at Mission. Daily readings from this gauge are available to interested parties via a toll-free telephone number. Due to the run-off from melting inland snows in April, the river level begins its annual rise from low winter levels. The rate at which the river rises increases throughout May, reaching its highest level in June and remaining up until the end of July or middle of August. At Mission, since 1962, the monthly mean water level for June is 4.0m above chart datum. The highest recorded water level in the same period was 6.1m. The Fraser River is affected by the tide as far upstream as Chilliwack.